Iron deficiency chlorosis in soybeans occurs in the northern U.S. in soils having a high pH. These soils are known as calcareous, high-lime or alkaline soils and they are especially prevalent in northern Iowa and southern and western Minnesota, important soybean growing areas. The condition is observed first as a yellowing of the trifoliate leaves and it results in a lowered yield.
Up to the present time the farmer has had two choices in dealing with this problem. He could choose seeds of a variety known to be resistant in some degree to the condition or he could spray the young plants with a foliar iron spray. The known resistant varieties often suffer from some other disadvantage and the application of foliar iron is both expensive and exacting. In fact, is it well known in the art that the best time to apply foliar iron spray is just before the leaves begin to yellow. Any degree of yellowing leads to reduced yield.